Observations on the feeding ecology of liza grandisquamis in Imo river estuary in southeastern Nigeria. – A. W. Akpan and R. G. Ubak
The feeding ecology of Liza grandisquamis from Imo River estuary (IRE) east of the Niger delta (Nigeria) was studied over a period of one year and collections were made from catches landed by fishers at Uta Ewa, Iko and Down Below fishing terminals. Analysis of stomach contents was undertaken using the relative frequency and points methods. The trophic spectrum showed that L. grandisquamis fed on a wide assortment of food resources. Index of relative importance (IRI) showed that L. grandisquamis primarily ingested diatoms, fine particulate organic matter (FPOM), diatoms, mud and sand and secondarily fed on coarse particulate organic matter (CPOM), preyfish, green algae and blue green algae. Macrophytic matter, free living nematodes, microarthropods and dinoflagellates were incidentally consumed. The spectrum of food dominance rank order gave: algae > detritus> sediments > macrofauna/meiofauna. L. grandisquamis exhibited considerable monthly/seasonal plasticity in dietary preferences with no significant differences in feeding intensity. Monthly dynamics in food richness depicted by the number of food items (Nf) showed minimum food richness in March and July (Nf = 24) and maximum in December (Nf = 35); FPOM, mud and diatoms were primary dietaries throughout the year. Seven major dietaries (CPOM, FPOM, mud, sand, diatoms, green algae and prey fish) constituted constant dietaries consumed monthly throughout the year while six dietaries (blue-green algae, red algae, dinoflagellates, micro -arthropods, free living nematodes and macrophyte matter) formed occasional dietaries consumed only in certain months. The consumption of a wide variety of food substances by L. grandisquamis shows high trophic flexibility and can be assigned to the algivore – detritivore – deposit trophic guild.